So I've been reading a lot about the EL70 and CHR-70. Besides teh construction details and $10 can someone break down the appreciable differences in performance between these two drivers?

The short version. Based on the same frame, the EL70, the CHR-70 is metal coned. Both are fairly neutral, but each tends a little bit towards the sterotypes for each material.The EL70 is also more efficient.

Preference will bend to your tastes, my personal preference tends towards the EL70 but i enjoy both (EnABLed of course ).